The present invention relates to paints and more particularly to an improved pigmented coating having water-displacing qualities for use upon metallic surfaces in humid environments to prevent corrosion.
Corrosion of metallic surfaces, particularly those of vehicles, such as aircraft, ships and automobiles, is an important concern of manintenance personnel because of the adverse effect on structural integrity and operating performance caused by corrosive deterioration. As a result, corrosion control procedures are steadfastly and regularly performed as part of an overall preventive maintenance program on such vehicles. When such vehicles are located in marine environments and subjected to the salt spray and high humidity associated therewith, corrosion control becomes even more critical a task and one which is made extremely difficult by the environmental conditions. A salt-laden atmosphere is highly corrosive, requiring that immediate attention be provided to cracked or chipped paint by recoating or touching-up the exposed bare metal substrate. When touch-up of the exposed areas is effected, moisture on or near the substrate, if not treated for removal, will cause voids in the applied coating and inadequate adhesion between the coating and the substrate, ultimately leading to additional corrosion and further maintenance problems.
Of the numerous coating compositions that have been developed to prevent corrosion of metal substrates, some have featured water-displacing qualities that facilitate their effective use in humid environments. These existing water-displacing coating compositions which generally contain corrosion inhibitors have been relatively effective in depositing clear, flexible, non-tacky films that act as physical barriers to corrosive elements. However, such film coatings have generally afforded only temporary protection, typically a maximum period of about sixty days, requiring frequent reapplications to prevent corrosion from attacking the metal substrate. While pigmented compositions have demonstrated more permanent coatings of the underlying metal, they have heretofore not possessed the level of water-displacement necessary for effective use in moist, marine environments, due to an adverse effect which pigmentation has evidenced on the water-displacing qualities of existing coating compositions.